Dimer species in dimethyl sulfoxide–water (80∶20 w/w) solution of N,N′-bis(salicylideneimine)-m-phenylenediamine (H2sal-m-phen) and similar Schiff bases with CuII, NiII, CoII and ZnII. Crystal structure of [Co2(sal-m-phen)2]·CHCl3‡

Abstract

Potentiometric studies were carried out in dimethyl sulfoxide–water (80∶20 w/w) at 25 °C and ionic strength 0.1 mol dm^–3 in NaClO₄ for the Schiff bases H₂sal-m-phen [N,N′-bis(salicylidene)-m-phenylenediamine], H₂sal-2,4-toluen [N,N′-bis(salicylidene)toluene-2,4-diamine] and H₂sal-2,6-toluen [N,N′-bis(salicylidene)toluene-2,6-diamine] and their complexes with Cu^II, Ni^II, Co^II and Zn^II. These studies have shown that monomer, dimer, ligand∶metal ratio 2∶1 and 1∶2 complex species are found. The first reported stability constants for these systems have been determined. The molecular structure of the complex [Co₂(sal-m-phen)₂]·CHCl₃ has been determined by single-crystal X-ray analysis. It consists of dimeric centrosymmetric units, with the two bis(salicylideneiminato)cobalt(II) residues bridged by two m-phenylene groups and with a chloroform molecule associated with each dimer molecule. The co-ordination geometry around each cobalt(II) can be best described as a distorted tetrahedron. Variable-temperature magnetic susceptibility measurements for the solid complexes [Co₂(sal-m-phen)₂]·CHCl₃, [Co₂(sal-2,4-toluen)₂]·4H₂O, [Co₂(sal-2,6-toluen)₂], [Ni₂(sal-m-phen)₂]·3H₂O, [Ni₂(sal-2,4-toluen)₂]·3H₂O, [Ni₂(sal-2,6-toluen)₂], [Cu₂(sal-2,4-toluen)₂] and [Cu₂(sal-2,6-toluen)₂] revealed a weak intradimer antiferromagnetic interaction.